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Water which is made of oxygen and hydrogen is the foundation for making an oxygen generator. Table salt is another key ingredient. As electricity is involved, you'll want to be very careful. The following link provides additional detail and how to steps. http://www.ehow.com/how_4739722_build-ox...
Then again, this answer might help you...
To build a Hydrogen-Oxygen generator you will need water, sodium hydroxide, two test tubes and holders, three large beakers, Hoffman voltameter, two leads, two test tube stoppers, nine volt battery and two rubber hoses. For more information look here: Homemade Hydrogen-Oxygen Generator http://www.ehow.com/how_5343517_build-hy...;

